Some seven million people are in urgent need of humanitarian aid due to the conflict in Syria, and more than $US4.4 billion ($A4.8 billion) is needed this year.
Of those needing help, more than two million have taken shelter outside Syria, while more than four million people have been displaced within the country, UN Emergency Relief coordinator Valerie Amos said.
"We are doing what we can but it is not enough," she told a conference in Kuwait, adding that UN agencies have 1000 staff on the ground, mostly Syrians.
She highlighted a wide hole in the funds available for humanitarian aid to the victims of the Syrian conflict.
"We need a total of $US4.4 billion for Syria and neighbouring countries just for this year. So far we have raised $US1.84 billion of that," said .
"The challenge we face is that the increased financial requirements for Syria could imply diverting funds from other very serious crises around the world," she said.
More than 110,000 people have been killed since the rebellion against the government of President Bashar al-Assad erupted in March 2011, according to activists.
